Great music and sound effects, very nice vibe overall. One piece of feedback for the future: the tutorial texts should be as straightforward as possible. "In an emergency an experienced diver may use his own air as a boost" is a nice flavor text, but it doesn't explain what I'm supposed to do. "Hold c to jump higher" is an actionable instruction - it should be there as well. Other than that, it was very fun and I could definitely see it becoming a full fledged game.